64 OLDHAM: THE STRUCTURE OF THE HIMALAYAS, ETC. 



depressed lower portion of the crust is as 10 to 04, except near 

 the northern margin where, in the last thirty miles or so, it falls 

 to about 3 of the effect produced by the trough. 



The figures which have been calculated for the particular 

 dimensions of trough considered, apply with proportionate variation 

 to any other dimensions of a trough of similar form, and the ratio, 

 between the effect of the superficial trough and of the depressed 

 lower surface of the crust, would not be materially altered. We 

 may, therefore, apply the results obtained to the conclusions, drawn 

 from observation, and find that the depth of the trough, deduced 

 from the deflections on the assumption that the whole effect is due 

 to it alone, would have to be reduced by about 14 to 20 per cent., 

 if the total effect is resolved into its two components, and that the 

 reduction would have to be about 28 per cent, in the case of the 

 gravity observations ; but apart from this there would be no 

 material alteration in the general form of the trough. Consequently 

 the adoption of this hypothesis of origin of the trough would not 

 lead to any modification in the conclusions drawn as to the general 

 form of the trough, though it would lead to a reduction in the 

 estimated depth of the alluvium by somewhere about one quarter, 

 at most, of the estimate which would be formed if the whole effect 

 was attributed to the trough alone. 



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